The present invention relates to an inline sifter, which is disposed in a pneumatic transportation line of a powdery material of, for example, a food product, a chemical product, or a medicinal product and sieves the powdery material.
One example of prior art inline sifters is shown in FIGS. 16 through 18. This inline sifter 301 is disposed in the middle of an air-driven transportation line. A vertical housing 302 is mounted on a stand 303. A cylindrical sieve 304 is fixed inside the housing 302 to have its axis in the vertical direction. An inlet 305 and an outlet 306 are arranged below the housing 302, and an air supply element 307 is disposed on the upper side of the housing 302. Four air nozzles 308 are suspended from the air supply element 307 to the inside of the sieve 304. The air is ejected from the air nozzles 308 at regular intervals, in order to relieve the clogging of the sieve 304. A high-pressure mixture of a powdery material and the air is pressed out of the inlet 305 and is fed into the sieve 304. After removal of aggregates of the powdery material and foreign substances by means of the air ejected from the air nozzles 308, the powdery material with the air flow, which has passed through the sieve 304, is discharged from the outlet 306. The aggregates of the powdery material and the foreign substances, which are not allowed to pass through the sieve 304, inversely flow through the inlet 305 and are taken out of a powder discharge port 309. The inline sifter is disposed in the middle of a gas-driven transportation line and is applicable to loose shipment equipment, blender-powder feeding equipment, dumping powder feeding equipment, and silo equipment.
Because of the structural limitation, the inlet 305 and the outlet 306 have bends of small curvatures. This structure undesirably increases the pressure loss. The powdery material in the housing 302 and the inlet 305 is naturally under the influence of gravity. The powdery material is to be pressed out against the gravity. This causes a large pressure loss in the housing 302 and the sieve 304. The inside of the housing 302 has a practically identical pressure, which is positive relative to the atmosphere. The structure of pressing out the powdery material has a large pressure loss and a low sieving efficiency and makes the sieve 304 easily clogged. The rough mesh of the sieve 304 may, however, cause insufficient removal of foreign substances.